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The head of Britain’s MI5 says Iran has made a “major shift” this year, now setting its sights on UK military sites, and calls last month’s suspected plot against RAF Fairford one piece of a wider Iranian campaign against “harder targets.”

Getting into it: In his annual threat speech Tuesday, MI5 Director General Ken McCallum said the Sept. 27 incident near the base, where US B-1 bombers had been stationed for strikes on Iran, was “not unique,” pointing to “other examples” of threats to military sites “not just in the UK but around the world, most particularly in Iran’s own region,” though he declined to give details. He said Iran-linked cases have led to more than 50 arrests in Britain over the last year, describing the shift as a step up from the arsons and stabbings Iran has previously farmed out to hired criminals, many of them aimed at Jewish communities.

Seven men have now been arrested over the Fairford incident, including five British nationals in their 20s stopped in three vans near the base and a British-Iranian dual national. All have been released on bail, and police say the vans turned up nothing but gasoline, with no explosives or drones. The US still moved its 12 B-1 bombers off the base after new intelligence warned of a possible drone strike. Iran has denied any involvement.

McCallum played down the immediate danger, saying what MI5 has seen of Iran in the UK has not been “anywhere near the level of capability” needed for a sophisticated strike on a base. He also said Russia “remains aggressor No. 1,” with Moscow escalating hybrid attacks across Europe while staying below NATO’s Article 5 threshold, adding that state threats now take up more of MI5’s resources than they did during the Cold War. He announced a new AI Threat Assessment Centre, warning that AI could help terrorists develop biological or chemical weapons.

This all comes a day after UK PM Andy Burnham told Parliament the Fairford plot was “almost certainly” directed by Iran’s Revolutionary Guard and vowed that “we will not tolerate these threats on our soil,” as his government sanctioned two Iranians it says helped direct attacks abroad.

It should be noted that Iran has denied targeting military infrastructure within the UK.